Fatal error: Call to undefined function get_plugin_data()

I tried again to use the plugin in my multisite with 2 sites in sub-directories (site and site/en/) with 2 activated plugins: Easy SMTP and Blue Admin. I need these 2 plugins and won’t abandon them. In your installation instruction you wrote: “Upload plugin-name.php to the /wp-content/plugins/ directory” Did you really mean the file plugin-name.php? But there is no such file. Is it user-upgrade-capability.php? But then what for are all other files? So I uploaded the whole plugin folder /user-upgrade-capability/ to /wp-content/plugins/. Was it wrong? I activated the plugin for network and was immediately redirected to the white screen with message: “Fatal error: Call to undefined function get_plugin_data() in /var/www/html/test-2/wp-content/plugins/user-upgrade-capability/user-upgrade-capability.php on line 311” I couldn’t enter the site anymore. Then I literally fulfilled your instruction and uploaded only the file user-upgrade-capability.php to /wp-content/plugins/. Of course I’ve got a white screen with error message. I didn’t try to activate the plugin for each site of multisite because the 1-st issue revealed it’s dangerous features. for the “Upload plugin-name.php to the /wp-content/plugins/ directory” you are right I’ll update that instruction its generic and not helpful, the easiest way in install is to pull the plugin from the WordPress plugin repository the final state should be ../wp-content/plugins/user-upgrade-capability/ <files in here> can you install it through the WordPress plugin repository “add plugins” automatic installer. So follow these steps.. 1) remove/delete the plugin folder you created manually (e.g. ../wp-content/plugins/ user-upgrade-capability / 2) Go to site dashboard ‘My Sites’ > ‘Network Admin’ > ‘Plugins’ 3) Click on the ‘Add New’ button 4) search for ‘User upgrade capability’ and install 5) Network Activate the plugin let me know if you get the same results. when you say “ I didn’t try to activate the plugin for each site of multisite because the 1-st issue revealed it’s dangerous features. ” the plugin is a network wide activation you don’t need to do this per site, once its active it will be active on each of the network sites. You simple start to use it on a site instance by configuring a reference site and away you go. FYI I’ve updated the install notes section.. https://wordpress.org/plugins/user-upgrade-capability/installation/ When plugins are installed through dashboard sites are 2-3 times slower than after manually unzipped folder uploading. I don’t know why but it is my experimental fact. So installation through dashboard is unacceptable for me. that doesn’t sound right, the site should not behave any different with either the auto/dashboard install or a manual upload of files. Both end up with php files and there is no difference. Have a look at separately re-installing WordPress again and seeing if the same behavior occurs on a fresh install. a good resource for de-bugging is by scribu https://github.com/scribu/wp-posts-to-posts/wiki/Troubleshooting This reply was modified 9 years, 3 months ago by Justin Fletcher . I installed WP above 100 times for myself and for my clients. And each time when I manually copied plugins in /wp-conten/ the DB was nearly 2 times larger (for example 1 Mb vs. 605 kb) but site worked 2-4 times faster than under dashboard installing (for example 0,75 c vs. 2,5 – 3,4 c for page loading). Never mind that “site SHOULD NOT behave any different”. It’s important that it really DOES. While installing plugins WP core makes changes in meta data, in DB. The method of installing influences on result. This reply was modified 9 years, 3 months ago by cronwerk . This reply was modified 9 years, 3 months ago by cronwerk . I’ll have to look at the database with both installations manual/auto at somepoint. Either way a manual install of the plug is fine if you prefer. so that would be here .. ../wp-content/plugins/user-upgrade-capability\readme.txt ../wp-content/plugins/user-upgrade-capability\uninstall.php ../wp-content/plugins/user-upgrade-capability\user-upgrade-capability.php ../wp-content/plugins/user-upgrade-capability\includes\class-tabbed-settings.php ../wp-content/plugins/user-upgrade-capability\includes\class-tgm-plugin-activation.php ../wp-content/plugins/user-upgrade-capability\includes\class-user-upgrade-capability-network-info.php ../wp-content/plugins/user-upgrade-capability\includes\plugin-install.php ../wp-content/plugins/user-upgrade-capability\includes\settings-general.php ../wp-content/plugins/user-upgrade-capability\includes\settings-upgrade-caps.php ../wp-content/plugins/user-upgrade-capability\includes\settings-upgrade-roles.php Thank you for consultation. Best regards.